GRK 36137 R4 #10 by 3-1/8-inch PHEINOX 316 Stainless Steel Marine Grade Fasteners Pro Pak (305 screws) 316 stainless Steel for the ultimate performance in all seaside construction Uses GRK T25 bit Self-tapping, countersinking head; w-cut thread design For use in wood, particle-board, cement fiberboard, plastic, wood decking, melamine and sheet metal